JPS61120862A - Coating method - Google Patents

Abstract

PURPOSE:To form a coating film at a low temp. in a short time, which has excellent durability, mechanical characteristics and solvent resistance, by applying a paint composed of a polyisocyanate resin and a ketimine compsn,. to a substrate and exposing the coated substrate to hot water. CONSTITUTION:A substrate is coated with a paint composed of a polyisocyanate resin (A) selected from among an isocyanate group-contg. copolymer contg. a monomer of formula I (wherein R is H, methyl) as a comonomer and a polyurethane resin obtd. by reacting a polyisocyanate of formula II (wherein n is 2, 3) with a polyhydroxy compd. and a ketimine compd. (B) wherein at least one amino group of a polyamine compd. contg. at least two primary groups per molecule is blocked by the reaction thereof with a ketone. The resulting coated substrate is exposed to hot water of a hot and humid environment to cure the paint.

Description

[Detailed Description of the Invention] There are horizontal paints and thermosetting resin paints that can reduce the productivity of line painting and improve the physical properties of the paint film such as physical strength, solvent resistance, stain resistance, and durability. From this point of view, thermosetting resin paints are superior to thermosetting resin paints in which resins react with each other to form infinitely large molecular weights, and thermosetting resin paints have been used in coatings that require high coating film quality. However, when thermosetting resin is used, sufficient thermal energy is required for the resin reaction, and if the heating temperature is lowered to reduce heat energy and energy, the reaction will take a long time. Sexuality decreases. In order to overcome this difficulty, a resin that reacts at a lower temperature is desired, but if the reactivity of the resin is increased, the pot life in the paint state will be shortened, resulting in significant restrictions on coating work. As a result of the emergence of a coating method that completes the curing reaction in a short period of time, it is possible to create coating films with excellent weather resistance, long-lasting durability, mechanical properties, solvent resistance, etc. at low temperatures. A polyvalent incyanate having a structure of an isocyanate (in the formula, n is 2 or 3) containing a monomer having a short time (in the formula, R is hydrogen or a methyl group) structure as a copolymerization component and a polyvalent hydroxy compound. At least one amino group of a polyvalent isocyanate resin selected from polyurethane resins produced by the reaction and a polyvalent amine compound having two or more 1- primary amino groups in the +tn- molecule. After applying a paint consisting of a ketimine compound sequestered by reaction with a ketone to a substrate, exposing the material to hot water or a high humidity environment for one time,
The material is characterized by hardening.

Examples of the monomer having the structure (group) which is an essential copolymerization component of the isocyanate group-containing copolymer which is the multivalent iso-iso-a-to resin of (A) above include p-impropenyl-α, α-Dimethylbenzyl isocyanate, m-
Impropenyl-α,α-dimethylbenzylisocyanate, p-ethylenyl-α,α-dimethylbenzylisocyanate 1m-ethylenyl-α,α-dimethylbenzylisocyanate)%'.

The proportion of these isocyanate group-containing monomers in the isocyanate group-containing copolymer is suitably 3 to 50% by weight, particularly preferably 10 to 30% by weight.

Ethylenically unsaturated monomers copolymerizable with the above monomers include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate.

2-ethylhexyl acrylate, lauryl acrylate, onyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate.

2-hydroquinethyl acrylate, 2-acrylic acid
Acrylic esters such as hydroxypropyl, methyl methacrylate, and ethyl methacrylate.

Propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, oleyl methacrylate, stearyl methacrylate, methoxyethyl methacrylate, butoxyethyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, methacrylate Acid tetrahydrofurfuryl.

2-hydroxyethyl methacrylate, methacrylic acid
Methacrylic acid esters such as 2-hydroxypropyl;
Aromatic vinyl monomers such as nutylene, α-methylnutylene, vinyltoluene, paramethylmethylene, monoalkyl esters or dialkyl esters of unsaturated dibasic acids such as maleic acid, fumaric acid or itaconic acid; acrylonitrile , nitrile group-containing monomers such as methacrylonitrile; pinyl enethers such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, and itaconic acid.

One or more types of unsaturated carboxylic acids such as crotonic acid are used. Among the above-mentioned ethylenically unsaturated monomers, Nisder acrylates and methacrylic esters are particularly suitable from the viewpoint of weather resistance and the like.

The isocyanate group-containing copolymer usually has a molecular weight of 2,000 to 2
It preferably has a number average molecular weight of 0,000, and can be used in solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization in an inert solvent in the presence of a polymerization initiator that generates radicals. Although it can be synthesized by any method, solution polymerization method (or bulk polymerization method) in a water-free system is particularly suitable for the purpose of using the coating composition of the present invention.

A polyurethane resin obtained by reacting another polyvalent isocyanate having the structure of (A) or a polyvalent hydroxy compound with a polyvalent hydroxy compound is α
, α, α′, α′-tetramethyl metaxylylene diisonanate, α, α, α′, α′-tetramethyl para-quinylylene diisocyanate, α, α, α′, α′, (1
', one or more polyvalent isocyanates such as f-hexamethylmenthylene triisocyanate and the following polyvalent hydroxy compounds are mixed in a ratio such that the isocyanate group is in excess equivalent to the hydroxyl group, and a polycondensation reaction is carried out. You can get it by going.

As the above polyhydric hydroxy compound, hydroxyl-terminated polyether, hydroxyl-terminated polyene ether, hydroxyl-terminated polycarbonate, etc. are preferable, and examples of the hydroxyl-terminated polyether include polyoxyethylene, polyoxypropylene, and polyoxyethylene propylene copolymer polyether. , polytetramethylene glycol, etc. are used, and in addition to simple linear polyethers, polyhydric alcohols such as glycerin and pentaerythritol, and polyhydric amines such as ethylenediamine are used in the skeleton, and three or more hydroxyl groups have a branched structure. These polyethers also include polyfunctional polyethers having at the molecular terminal.

In addition, examples of the hydroxyl-terminated polyester include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol,
Butanediol, ■, 3-butanediol, bentanediol, 1,6-hexanediol, dodecanediol, polyethylene glycol, polypropylene glycol, polydetramethylene glycol, neopentyl glycol.

2,2.4-trimethylbentanediol, hydrogenated bisphenol A, propylene oxide adduct of bisphenol A, glycerin, trimethylolethane, trimethylolpropane, pentaerythri) -/l/,
) +) Polyhydric alcohols such as hydroxyethyl isocyanurate and, for example, phthalic anhydride.

Isophthalic acid, terephthalic acid, dimethyl terephthalic acid,
Succinic acid, adipic acid, azelaic acid, dodecanniic acid,
Icosanniic acid, dimer acid, maleic anhydride, fumaric acid, itaconic acid, tetrahydrophthalic acid, hexahydrophthalic anhydride, hymic anhydride, methylnadic anhydride, trimellitic anhydride, pyromellitic anhydride, butanetetracarboxylic anhydride Examples include those obtained by condensation reaction with a polyhydric carboxylic acid such as an acid, a polycarboxylic acid anhydride, or an alkyl ester of a polyhydric carboxylic acid at a mixing ratio with an excess of hydroxyl groups. In addition, in this case, monobasic acids such as fatty acids, benzoic acid, and tanyabutylbenzoic acid, octatool, lauryl alcohol,
Monoalcohols such as oleyl alcohol or, for example, human-roxystearic acid, parahydroxybenzoic acid.

Oxycarboxylic acids such as metahydroxybenzoic acid may be used in combination. Polycaprolactone, which is a ring-opening polymer of ε-caprolactone, is also extremely useful. or,
Examples of the hydroxy-terminated polycarbonate include polyhexamethylene carbonate and polytetramethylene carbonate.

Additionally, hydroxyl-terminated polyethers as described above.

The polyhydric alcohols exemplified as raw materials for the hydroxyl-terminated polyester may be used in combination with the hydroxyl-terminated polyester and hydroxyl-terminated polycarbonate, but the average molecular weight of the polyvalent hydroxyl compound described above is determined by the organic solvent of the poly and phrethane resin produced. The range is preferably from 200 to 5,000, particularly preferably from 300 to 2,000 from the viewpoint of solubility and reactivity.

The polyvalent incyanate used in the present invention is obtained by polycondensing the above-mentioned polyvalent isocyanates that give an excess equivalent of incyanate groups with respect to the hydroxyl groups of the above-mentioned polyvalent hydroxy compound under heating conditions of usually 40 to 150°C. The resin is obtained, and the ratio of hydroxyl groups to isocyanate groups is usually in the range of 1:1.3 to 1:2.5, preferably 1:1.5 to 1:2.0 in terms of equivalent ratio. be.

f which is an essential component of one of the components used in the coating method of the present invention
Component B), that is, a ketimine compound in which at least one amino group of a polyvalent amine compound containing two or more primary amino groups in the molecule is blocked by reaction with a ketone, is, for example, ethylenediamine. , trimethylene diamine, tetramethylene diamine, hexamethylene diamine,
Aliphatic amines such as nonamethylene diamine and dipentene diamine, ring group diamines such as isoborone diamine, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylpropane, hydrogenated xylylene diamine, and dipentene diamine; α, α, α′.

α'-tetramethylxylylene diamine, xylylene diamine, etc., where the amino group is not directly bonded to the aromatic ring.
- Polyvalent amines such as diamines can be obtained by dehydration reaction with ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone. Aromatic amines such as methylene dianiline have poor weather resistance and are therefore unsuitable as raw materials for the ketimine compound of the present invention. Although it is desirable that all the amino groups of the polyvalent amine compound be ketiminated, it can be used in the present invention if at least one amino group in one molecule is ketiminated.

The above-mentioned mixing ratio of the ketimine compound (polyvalent isocyanate resin of Al and fB) is the equivalent of the isocyanate group of (A) and the amino group of the ketimine compound of (B) (total of ketimine and free amino groups). The equivalent of 1:0.6-1:
They are mixed and used in a weight ratio of 1.2, particularly preferably 1:0.7 to 1:1.

The polyvalent isocyanate resin fA+ and the ketimine compound fB) are usually dissolved in water or an organic solvent that does not contain active hydrogen, and are used as a transparent rear face. [Various coloring pigments such as carbon black and phthalocyanine blue, such as calcium carbonate, barium sulfate, talc, alumina, and silica.

It can be put to practical use by mixing and dispersing inorganic fillers such as glass fiber and bentonite, as well as auxiliaries such as a leveling auxiliary agent and a defoaming auxiliary agent 9 and a dispersion auxiliary agent.

The paint obtained as described above has a long pot life of 30 hours or more at room temperature. The paint prepared as described above can be used, for example, on metals, plastics, slate, wood materials, cement-based moldings, leather, and paper.

It is applied to various substrates such as textiles, and the coated article is then immersed in warm water or exposed to a high humidity environment. At this time, it is preferable to evaporate the organic solvent in the paint film and then expose it to hot water or a high humidity environment because the paint film is less likely to shrink, but such abnormalities in the paint film may occur. The phenomenon depends on the type of substrate and the thickness of the coating film, and there is no problem even if organic solvents remain in the coating film.
! It is sufficient that the amount of organic solvent in the coating film at the time of g is 20% by weight or less.

Therefore, in line coating, it is advantageous to pass through a drying zone to reduce evaporation of the organic solvent in the coating film in order to improve productivity.

Next, the painted object is immersed in warm water (40 to 100°C) or
Or exposed to a high humidity environment with a relative humidity of 80% or more, preferably 90% or more. Regarding the temperature conditions in a high humidity environment, the exposure time can be shortened if the temperature is higher, so the most common temperature is around 50-80℃, but even 100℃
The above water vapor may be directly sprayed onto the object to be coated, or the object to be coated may be placed in an autoclave.

The duration of immersion in hot water or exposure in a high humidity environment depends on the temperature and the thickness of the coating, and even if the coating is not completely cured in the line, trace amounts of moisture penetrating into the coating or moisture from the outside air may This reduces the required thermal energy, which varies depending on whether curing is allowed after removal from the line, and does not reduce productivity, and also reduces the pot life of conventional urethane paints. This is an innovative coating method that can overcome restrictions, and the coating film obtained by this coating method has excellent durability such as weather resistance and moisture resistance, mechanical properties,
Excellent solvent resistance, etc.

The present invention will be specifically explained below with reference to Examples.

Example (1) Synthesis of incyanate group-containing copolymer 800 parts by weight of toluene and 200 parts by weight of methyl isobutyl ketone were placed in a reactor equipped with a stirrer, a reflux condenser, a thermometer and a dropping tank, and the mixture was heated to 85°C. After heating, a mixture of each monomer and polymerization initiator shown in each experiment number in Table 1 was added dropwise from the dropping tank over 4 hours, and the reaction solution was heated to 85% while stirring.
The temperature was maintained at ~90°C, and at the end of the dropwise addition, 8 parts by weight of azobisisobutyronitrile as a polymerization initiator was further added, and the reaction was continued at the above temperature for 4 hours to obtain a solution of the isocyanate group-containing copolymer. Ta.

Table 1 shows the solid content, viscosity, and isocyanate group content (equivalent/) of the copolymer solution layer obtained in each experiment number.
100O is also described.

Table 1 Note: All numbers for each ingredient are parts by weight.

(2) Synthesis of isocyanate group-containing polyurethane resin A reactor equipped with a stirrer, a reflux condenser, and a thermometer was charged with the polyvalent isocyanate, polyvalent hydroxyl compound, and solvent shown in each experiment number listed in Table 2 at 110°C. The mixture was heated and stirred for 6 hours to react, thereby obtaining a solution of an isocyanate group-containing polyurethane resin. Table 2 also lists the solid content, viscosity, and isocyanate group content (equivalent/solution 1000F) of the polyurethane resin obtained in each experiment number.

Table 2 Note: All numbers for each ingredient are parts by weight.

(3) Synthesis of ketimine compound Into a reactor equipped with a stirrer, a condenser with a water separator, and a thermometer, prepare the polyvalent amines, ketones, and other raw materials of each experimental symbol (A) to +C) shown in Table 3. , Table 3
The reaction was carried out for 8 hours at the temperature shown in .

In experiment symbols fA+ and (B), the solvent was refluxed and the generated water was separated and removed, and in experiment symbol (C), the generated water was adsorbed and removed on the molecular sieve, and the molecular sieve was separated after the reaction. A reactant was obtained. Furthermore, the reactants of each experimental symbol were concentrated under reduced pressure and adjusted to a 50% solution. The conversion to ketimine was determined by nuclear magnetic resonance analysis and the total amino group content of each reactant solution (the total amount of ketimine and free amino groups was determined by
(expressed as the number of equivalents in 00 g) was measured by hydrochloric acid titration and is also listed in Table 3.

Table 3 (4) Polyvalent isocyanate resin solution 2 of each experiment number (1) to (6) in Table 1 and Table 2 described in Paint Preparation Examples (1) and (2)
00 parts by weight and 100 parts by weight of titanium oxide, 100 parts by weight of toluene and 50 parts by weight of ethyl acetate as solvents, and 0.1 parts by weight of a silicone leveling agent were mixed, dispersed in a sand mill for 1 hour, and discharged to obtain each polyvalent A pigment dispersion of incyanate resin was obtained.

Next, each ketimine compound solution of (A) to fc) in Table 3 described in Example (3) was added to 45 parts by weight of each of the above pigment dispersions in the proportions shown on the back side, respectively, in the weight proportions shown in Table 4. Mix and prepare paints from fT) to 1.

Table 4 (5) Painting and curing of paint film-1- Each of the above-mentioned paints (I) to M was spray-painted on an alumite-treated aluminum plate so that the dry film thickness was about 30 μm. After heating in a hot air dryer at 40'C for 5 minutes to evaporate part of the solvent, immediately dry at 40'C and 60
The coated plates were placed in a humid box with a relative humidity of 95% at 0G and 80'C, and in hot water at 60'C for the times listed in Table 5, and immediately after taking them out, the coated surfaces were rubbed with gauze soaked in methyl ethyl ketone to ensure a cured state. Number of times until the paint film peels off 1. Judgment was made by IC.

In addition, as a comparative example, a coated plate was left in a constant temperature chamber at 80° C. and relative humidity 60%, and the same judgment was made. The gel times at 20°C of paints (I) to (X'I) were as follows.

Paint (1) 52-hour paint fTTl 40-hour paint fTTl1 64-hour paint ■ 45-hour paint 1) 60-hour paint Surface 46 hours Paint cured for 80 minutes at 80°G and 95% relative humidity The physical property evaluation results of the membrane are listed in Table 6.

(6) Painting and curing of coating film - (2) - Applying the above paints fT) to (to) on a galvanized steel plate using a roll coater so that the dry film thickness is about 15μ,
After heating with a hot air dryer at 200° C. for 1 minute, it was immediately cooled by showering with water. The difference in the hardening state of the coating film when it is cooled with a water shower and when it is air-cooled without a water shower is determined by the solvent resistance by methyl ethyl ketone (see (5) above).
(same as above). The results are shown in Table 7.

Table 7 As a control, a paint consisting of a hydroxy-functional acrylic resin and a melamine resin was applied in the same manner and cured in a hot air dryer at 200°C for 1 minute and in a hot air dryer at 260°C for 1 minute. The temperature is 5 times at 200℃, 260℃
It was 35 times at ℃.

Claims (1)

[Claims] 1. (A) General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼(
An isocyanate group-containing copolymer containing a monomer represented by hydrogen or a methyl group (in the formula R is hydrogen or a methyl group) or a general formula ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ (in the formula,
n is 2 or 3) A polyvalent isocyanate resin selected from polyurethane resins obtained by reacting a polyvalent isocyanate with a polyhydroxy compound, and (B) two or more primary amino groups in one molecule. After applying to a substrate a paint consisting of a ketimine compound in which at least one amino group of the polyvalent amine compound containing is blocked by reaction with a ketone, the painted object is exposed to hot water or high humidity environmental conditions. A coating method characterized by curing the paint.